Recently visited the Dargah Shareef of Khwaza Moinuddin Chisti. I think it is a very special place indeed. Not entirely for spiritual reasons but also because of its significance in the spread of Islam in the Indian subcontinent.

If you are in Ajmer don,t forget to visit the Adhai-din-ka-jhonpra, a former jain temple converted into a mosque by Qutub Aibak( i think it's the same guy who did the Qutab Minar). About forty columns support the roof, but no two are alike. Seeing this makes you realize the vigour and creativity of the early Islamic builders. Sadly, today you are hard pressed to find the same level of mature taste and ingenuity in Islam.